NTPC's shares crashed 11.81 percent to Rs 135.15 on the BSE. At the NSE, the stock tumbled 12 percent to Rs 135.

The scrip was the top loser among the blue-chips on both Sensex and Nifty.

Weakness was seen in other power related stocks, including NHPC which was trading lower by 1.64 percent, Power Grid slipped 3.40 percent and SJVN was down 0.96 percent at the BSE.

CERC has issued draft regulations for tariff determination during FY15-19 applicable for government companies.

"We see huge negative impact for NTPC. However, we see lower impact for PGCIL, NHPC and SJVN," brokerage firm Emkay Global said in a report.

"The final regulations could be different from the draft as has happened in the past. However, given the quantum of negative impact is high compared to previous draft regulations even if the norms are relaxed a bit it would still be negative," the report added.

"The draft CERC regulations have just come in public domain and we are studying the same. Prima facia we find positive changes. This paper is under discussion and we are going through with a fine comb before it is finalised. We would like to assure our investors our continued returns and thank them for their support," NTPC said in a statement.